1. Field of the Invention
The present invention relates to automatic welding apparatuses and, in particular, to an apparatus for automatically cleaning the gas nozzle and refinishing and/or replacing the welding tip of a robotic welding apparatus.
2. Description of the Invention Background
In various environments, it has proven expedient to employ an automatic apparatus for accomplishing the welding of articles to be joined. A particular welding apparatus that has achieved considerable commercial success is known as a gas MIG automatic welder. In such an apparatus, a robotic arm is employed to move a welding head which comprises a contact or weld tip through which weld wire continuously passes to feed an arc welding process. Typically, a gas nozzle is provided on the robot arm in surrounding relation to the weld tip in order that inert gas may be applied around the weld tip and to the weld site during welding to avoid the inclusion of contaminants in the weld. As such, the robot arm moves the weld tip along the intended weld area while welding wire is being fed therethrough to the weld site and inert gas is caused to flow over the weld site.
A particularly troublesome problem which has arisen in connection with such automatic welding apparatuses is the development of weld spatter around and inside the gas nozzle and around the weld tip. The weld spatter is a hard material which is generated during the welding process and which collects on these surfaces and is known to build up to a considerable degree if not removed periodically. Spatter can restrict the gas flow between the gas nozzle and the weld tip and thereby prevent a complete shielding of the weld site by the inert gas. Spatter can also build up on the weld tip to a point at which weld wire feed is impeded and the arc welding process is damaged. If the build-up continues to excess, a complete breakdown of the welding process may be caused by the spatter. While anti-spatter compounds are available for spray application to the gas nozzle weld tip, they serve only to delay the deposition of spatter, not to prevent it.
In an initial effort to correct the problems caused by weld spatter, operators of automatic welding apparatuses were forced to halt the welding process in order that the gas nozzle and the weld tip could each be manually removed and cleaned. Obviously, this activity was time-consuming and grossly inefficient and the enhanced productivity to which the automatic apparatus was directed was lost due to the required manual cleaning of the gas nozzle and weld tip. In those environments in which several robotic welders are used simultaneously either a worker was forced to enter a most hazardous area or all such welders had to be halted in order that the gas nozzle and/or welding tip of one welding arm could be cleaned.
In one apparatus, it was attempted to automatically conduct certain cleaning operations relating to the gas nozzle and welding tip. In that apparatus, the gas nozzle was physically restrained by the cleaning apparatus and a formed milling tool was employed to mill the weld spatter from the exterior surface of the gas nozzle and from portions of the weld tip. There, a hydraulic motor was employed to grasp the gas nozzle and a vertical hydraulic cylinder was used to move a milling apparatus rotated by a rotating hydraulic motor into engagement with the weld tip and gas nozzle. Thereafter, anti-spatter compound was sprayed on the gas nozzle and welding tip.
Certain shortcomings have been encountered with the maintenance apparatus described above. First, due to the design of the clamping means which grasps the welding head, damage may occur to the welding head during clamping. Second, each configuration of gas nozzle and welding tip required its own cutter to mill the appropriate surfaces of the gas nozzle and welding tip. The maintenance of a battery of cutters to accommodate each welding tip--gas nozzle configuration proves costly. In addition, due to the limitations of milling apparatuses, milling was not possible on the entire inner surface of the gas nozzle which surface is precisely that upon which spatter normally collects and restricts gas flow. Further, again due to the limitations of the milling cutter, the entire weld tip was not able to be effectively cleaned from spatter. In addition, the previous apparatus had no means for removing the gas nozzle and replacing one weld tip with another.
Accordingly, the instant invention is directed toward an improved apparatus for cleaning the gas nozzle and weld tip of an automatic welding apparatus which overcomes, among others, the above-discussed problems and which provides a cleaning apparatus which is effective in the cleaning of gas nozzles and the cleaning and/or replacement of weld tips yet does not require a lengthy shutdown of welding apparatus operations.